Opposite pairs form ionic bonds, due to this the answer is D - Li and Br; They have unlike charges.
Answer:
2 litres of pure alcohol will be added to make the overall concentration of 9 litres of mixture as 30%.
Explanation:
Suppose x is the number of litres added to the 10% mixture than the quantity of new mixture is given as below
litres
litres
Also the quantity of alcohol is given as
Now the equation is as

So 2 litres of pure alcohol will be added to make the overall concentration of 9 litres of mixture as 30%.
n propene molecules == polymer (polypropene)
<u>Question in English : </u>
<span>
<em>An atom X has 8 neutrons and its atomic number equals 8. Knowing that this atom is isotopes of Y, which has mass number 18, answer: What is the number of neutrons in atom Y?</em>
</span><span><u>Answer :</u>
</span>Isotopes are defined as the atoms which have same number of
protons but different number of neutrons of same element. Since the proton
number is same, the atomic number also same. Hence the atomic number of Y is 8.
Mass number = atomic number + neutron number
18 = 8 + neutron number
Neutron number = 10
Hence, there are 10 neutrons in Y.